SeaFlux

The need for high resolution, accurate surface turbulent fluxes (heat, water vapor, momentum) over the global ocean has been articulated by numerous groups within the global climate community, including the WCRP JSC/SCOR Joint Working Group on Air/Sea Fluxes, the GEWEX Data and Assessment Panel (GDAP), and the CLIVAR SSG. Specific applications of such a dataset, together with a comparable surface radiation flux and precipitation datasets, would include:

• constraining the budget and mean transports of heat and fresh water in the global ocean
• diagnosing regional and time variations of the coupled atmosphere-ocean system
• evaluating the surface fluxes in coupled atmosphere-ocean models and weather forecasting models
• providing surface forcing for ocean models

Several efforts are underway to prepare ocean surface turbulent flux datasets, including the following. The Hamburg Ocean Atmosphere Parameters from Satellite Data (HOAPS) dataset has been prepared at a resolution of 50 km and 1 day for almost 20 years. Efforts have been undertaken for TOGA COARE to resolve the diurnal cycle of the surface fluxes. Based on the initial success in determining these fluxes at high resolution, the GEWEX Data and Assessment Panel has requested that we explore producing and evaluating a high-resolution, satellite-based surface turbulent flux dataset for the global ocean for a multi-year period. Also, the following recommendation was made in the report from the first meeting of the JSC/SCOR Joint Working Group on Air/Sea Fluxes:

“Cases exist where, following development of an algorithm for determining surface flux related information from satellite data, support has not been available for the application of that algorithm to developing a flux climatology. Therefore the Working Group recommends that the development of surface flux related climatologies based on the latest satellite algorithms be supported so that the quality of such algorithms be fully evaluated and the best climatology identified.”

While major efforts are presently underway to produce comparable datasets for the surface radiation fluxes (GEWEX Surface Radiation Budget Project) and precipitation (GEWEX Global Precipitation Climatology Project), there has been no parallel effort to evaluate the different techniques for determining the surface turbulent fluxes.

To rectify this deficiency, we originally proposed and convened two workshops (summers of 1999 and 2000) with the following goals:

• assess the present status of turbulent surface flux algorithms, including satellite-derived and NWP-produced sources for the input variables to these algorithms, existing satellite-derived datasets and algorithms, and suitable in situ validation datasets
• conduct an intercomparison of ocean surface flux analyses (including input variables and flux models) with each other and with in situ observations
• recommend the best algorithms (input variables, flux models) for a trial data analysis project to produce a one-year global ocean surface turbulent flux product (based upon satellite data, possibly combined with other conventional data)

The first workshop reviewed the analysis methods and datasets currently available and organize the intercomparison activity. The second workshop reviewed preliminary results of comparing various analyses and determine final comparison procedures leading to recommendations for how to conduct the pilot data analysis project. Results of both workshops were presented at annual meetings of the GEWEX Data and Assessment Panel and the JSC/SCOR Working Group on Surface Fluxes. During the trial data analysis project, the resulting one-year dataset will be examined in the context of the following integral constraints: global heat/water balance, meridional heat and freshwater transports, and heat/water balance in enclosed seas. As the results warranted, a data analysis project has been organized to produce a high-resolution, multi-year ocean surface flux dataset similar to other GEWEX datasets (e.g., ISCCP, SRB, GPCP). The SeaFlux product is now available.